When an operator assigns logical volumes in a storage system to servers, the operator performs assignment (i.e., mapping) of each of the logical volumes to one of the servers. The mapping is performed in accordance with the following procedure: firstly, zones, each of which is a group of gathered LUNs, are created so that the zones correspond to the servers, respectively; and secondly, the logical volumes are mapped to the LUNs, respectively, for every zone created, wherein the LUNs are pieces of identification information, each of which corresponds to a logical volume and allows the server to recognize the corresponding logical volume. By mapping between the LUNs and the logical volumes, respectively, in this manner, it is possible for each of the servers to access, via its own LUNs, respective logical volumes mapped to the LUNs.
A specific example will be hereinafter described with reference to FIG. 9 and FIG. 10.
In FIG. 9, an example of a list of logical volumes managed in a storage system, which is configured to be connected with two servers (i.e., servers 101 and 102), is depicted. Let us denote, hereat, a piece of identification information associated with a logical volume corresponding to a numeric value “xyz” by “LV xyx”. Moreover, let us assume, for example, that, in the storage system shown in FIG. 9, there are managed logical volumes corresponding to numerical values from 100 to 115, and further, there are LV 100, LV 101 and LV 110 to LV 112 to be assigned to the server 101, and LV 114 and LV 115 to be assigned to the server 102.
So that the servers 101 and 102 can recognize logical volumes assigned to themselves, it is necessary to perform mapping in the servers 101 and 102, respectively, between device names managed by the servers 101 and 102 and the logical volumes. In FIG. 10, respective correspondence relations ranging from the device names to the logical volumes are depicted. Firstly, in each of the servers 101, 102, correspondences 1011, 1021 between the device names and LUNs are managed in such a manner that, on recognition of a LUN, the server automatically creates a device name corresponding to the LUN; and secondly, in the storage system, correspondences between the LUNs and the LVs (i.e., pieces of identification information associated with the logical volumes) are managed. Moreover, Zone #1 and Zone #2 in the storage system correspond to the server 101 and the server 102, respectively.
Hereinafter, let us denote a LUN corresponding to a numerical value “a” by “LUN a”. A management table 103 includes Zone #1 1031 and Zone #2 1032. Then, in Zone #1 1031 of the storage system, LUN 0 and LUN 1 correspond to LV 100 and LV 101, respectively. Similarly, LUN 2, LUN 3 and LUN 4 correspond to LV 110, LV 111 and LV 112, respectively. Further, in Zone #2 1032 of the storage system, LUN 0 and LUN 1 correspond to LV 114 and LV 115, respectively.
On the other hand, it is recognized by the server 101 that device names /sda and /sdb correspond to LUN 0 and LUN 1, respectively, and similarly, device names /sdc, /sdd and /sde correspond to LUN 2, LUN 3 and LUN 4, respectively. In addition, the LUNs of the server 101 correspond to those of Zone #1, respectively. In the case of the server 102, similarly, /sda and /sdb correspond to LUN 0 and LUN 1 of Zone #2, respectively.
In accordance with the correspondence relations described above, for example, when the server 101 accesses data stored in the logical volume LV 110, the server 101 can achieve this access via its own device name /sdc. In this manner, the server 101 can also access logical volumes LV 100 to LV 112 via its own device names /sda to /sde, respectively. Similarly, the server 102 can access logical volumes LV 114 and LV 115 via its own device names /sda and /sdb, respectively.
Further, a process of allowing a user to actually use logical volumes is as follows: firstly, starting-up (or rebooting) of each of the servers is performed by the user, or a dynamic recognition of correspondences between the device names and the LUNs is executed by each of the servers; and secondly, a predetermined command, given by the user, or automatically issued by the server, is executed by each of the servers, and thereby, the logical volumes are incorporated into a file system of each of the servers.
Moreover, in the related art, an information processing system, in which, in the fabric on a storage area network (SAN), in the case where a regular-volume is deleted, or a regular-volume and a sub-volume are interchanged, by providing a virtual server for volumes, it is possible to recognize anew a regular-volume after the interchange, is disclosed, for example, in Japanese Laid-Open Patent Application Publication No. 2007-102512. Further, a storage apparatus, in which, an exclusive process performed by an upper-level apparatus is made unnecessary, and further, it is possible to retain an exclusive control condition in the storage apparatus, is disclosed, for example, in Japanese Laid-Open Patent Application Publication No. 2001-249769.
However, once an alteration (i.e., a deletion of a piece of identification information associated with a logical volume) occurs in the mapping information under which a user accesses logical volumes, the correspondence relations in the mapping information are likely to be broken.
For example, in the case where in-operation recognition of LUNs by the server 101 and correspondence relations between the LUNs and the logical volumes are as shown in a table of FIG. 11A, named as “Correspondence Relation at Commencement of Operation”, let us assume a case where a user regards LV 101 as being unnecessary because of certain reasons, and tries to remove LV 101 from the target of operation. Then, operations performed by the user under this assumption are as described below.
Firstly, the user removes /sdb from the file system by using a predetermined command or the like, and secondly, the user deletes LV 101 included in Zone #1. (Refer to a table of FIG. 11B, named “Deletion of LV 101”)
Moreover, once the restarting of the server 101 is performed by the user, or the dynamic rerecognition is executed by the server 101, subsequently, it results in discrepancies occurring in the correspondences between the device names and the LUNs due to the deletion of LV 101, as shown in a table of FIG. 11C, named “After Restarting or Dynamic Rerecognition”. Under such a condition that discrepancies have occurred in the correspondence relations (i.e., under such a condition that discrepancies occur in recognition of LUNs), once a logical volume having any discrepancy in correspondences to a LUN is accessed, it will probably result in data stored in the logical volume accessed being destroyed.
Moreover, even if the user does not delete LV 101, which is now out of use, but leaves it in Zone #1 so as to prevent the discrepancies in recognition of LUNs by the server 101, it does not lead to effective utilization of a logical volume corresponding to LV 101 for other purposes, for example, a utilization by other servers, such as the server 102.